Is Dirt the new Prozac?

Even if you don’t love gardening, digging in the dirt may be good for your health — and it has nothing to do with a love of nature or the wonder of watching things grow. The secret may be in the dirt itself: A bacteria called Mycobacterium vaccae that acts like an antidepressant once it gets into your system.

That’s right. A living organism that acts like a mood-booster on the human brain, increasing serotonin and norepinephrine levels and making people feel happier. It was accidentally discovered about 10 years ago, when Dr. Mary O’Brien, an oncologist at the Royal Marsden Hospital in London, tried an experimental treatment for lung cancer. She inoculated patients with killed M. vaccae, expecting the bacteria — which is related to ones that cause tuberculosis and leprosy — to boost their immune system. It did that, The Economist reported in 2007, but it also improved her patients’ “emotional health, vitality, and general cognitive function.” Later experiments with mice confirmed the bacteria’s effects; the study was published in a 2007 edition of the journal “Neuroscience.”

“These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health,” the mouse study’s lead author, neuroscientist Dr. Christopher Lowry, said. “They also leave us wondering if we shouldn’t all be spending more time playing in the dirt.”

“We believe that prolonged exposure to [M.vaccae] from childhood could have a beneficial effect,” he added.

It raises the intriguing idea of a future where doctors could treat clinical depression or Seasonal Affective Disorder with a simple vaccine (and possibly a future in which kids don’t need quite so may baths). In the meantime, people seeking a bit of a boost may be able to find it in their own backyards.

In an article in The Atlantic , author Pagan Kennedy tests out the ultimate in eco-friendly antidepressants herself. “As I huff the soil, I have no way of knowing exactly how much M. vaccae is floating into my lungs — or whether it’s enough to change my mind,” she writes. “But I sure can smell this compost.”

Mechanism:

According to Neuroscience treatment of mice with a ‘friendly’ bacteria, normally found in the soil, altered their behavior in a way similar to that produced by antidepressant drugs.

Interest in the project arose after human cancer patients being treated with the bacteria Mycobacterium vaccae unexpectedly reported increases in their quality of life. Lowry and his colleagues reasoned that this effect could be caused by activation of neurons in the brain that contained serotonin.

When the team looked closely at the brains of mice, they found that treatment with M. vaccae activated a group of neurons that produce the brain chemical serotonin. The lack of serotonin in the brain is thought to cause depression in people, thus M. vaccae’s effects on the behavior of mice may be due to increasing the release of serotonin in parts of the brain that regulate mood.